The present invention relates to an apparatus for trimming and forming the leads of multi-lead electronic components such as dual in-line package (DIP) IC components and for detecting the proper insertion of the leads into a circuit board.
DIP components comprise parallel rows of leads projecting from each side of the component, with anywhere from two to twenty individual leads in each row. In high volume, mechanized population of circuit boards with electronic components, there exists a need for trimming the excess portions of the leads which extend through the circuit board and bending or forming (clinching) the remaining portions of the leads to the underside of the circuit board prior to soldering, such as by flow soldering. If a lead has been misinserted, continued population and processing of the circuit board would be a waste of valuable time and effort. Accordingly, the instant invention provides means for detecting a misinserted lead, during the forming thereof, such that a programmed controller for the overall operation may receive information regarding the misinsertion and halt or change the processing of the circuit board according to the particular program used.
Of the above-referenced prior art, only U.S. Pat. No. 4,286,379 provides means for detecting whether or not all of the leads of DIP-type components have been inserted properly into a circuit board. This reference teaches the detection of properly inserted leads during the forming or clinching of the leads to the underside of the circuit board. Plural pivotal forming or clinching levers, one for each lead, are provided with apertures through which light-emitting elements may communicate with light-receiving elements when the levers have been properly displaced by engagement with properly inserted component leads. When a lead is not properly inserted, i.e., does not extend below the circuit board, this lever displacement does not occur and the respective lever will block light transmission to provide an indication of an improperly mounted component. The complexity of the forming and detecting head of this prior art prevents, or at least limits, any provision for lead trimming, as exemplified by the lack of any reference thereto in the disclosure. Furthermore, the spring means which biases each lever into proper position, prior to lead engagement, presents an engineering design problem in that the leaf material from which it is made must be very light, when used with soft leads, to assure a positive displacement or deflection of the levers by the soft leads; thus, without constant cleaning of the tooling assembly, any contamination buildup therein can affect these springs as well as the photosensors.
The above-referenced U.S. Pat. No. 4,218,817 discloses a pair of pivotal trimming and/or forming arms having stress detecting elements attached thereto for detection of a properly inserted lead upon engagement of an arm therewith. This reference does not address the problem of dealing with multi-lead components such as DIPs. Although not disclosed, adaptation of the teaching of this prior art reference to such multi-lead components would necessitate the provision of a pivotal arm for each lead of the component, thus increasing the complexity of such a tooling assembly.
The above-referenced Japanese Patent Laid-Open No. 74989/1981 also does not contemplate or disclose a solution to the problem of dealing with multi-lead components, and the teaching therein presents the same adaptation complexity in solving this problem as that of U.S. Pat. No. 4,218,817.
It is an object of the present invention to provide an apparatus, which is relatively uncomplicated in structure and reliable in function, for detecting the presence or absence of each lead of a multi-lead component such as a DIP.
It is a further object of the invention to provide such an apparatus which is easily maintained and replaced.
It is a further object of the invention to provide an apparatus which, although particularly useful in the trimming, forming and detecting of multi-lead components such as DIPs, is also useable with radial lead or axial lead components which have been inserted into a circuit board or the like.
It is a further object of the invention to provide a lead trimming, forming and detecting means in which the angle of forming or clinching of the remaining portion of the lead to the underside of the circuit board is adjustable.
In accomplishing these objectives, as well as other objectives which will become apparent from the following disclosure, the instant invention provides a head assembly having a pair of anvils fixed relative to the head assembly, one anvil for each row of leads, and a pair of cutting and forming arms moveable relative to the head assembly such that each cutting and forming arm cooperates with a respective anvil by engaging and driving all of the leads of one row into engagement with the anvil and, during passing of the cutting and forming blade across the anvil, trimming excess portions of the leads and forming or clinching the remaining portions of the leads to the underside of the circuit board. During the forming portion of the operation, the cutting and forming arms drive the remaining portions of each properly inserted lead into engagement with a respective electrical contact finger to provide a ground and complete an individual circuit for each contact finger. Ground for the circuit corresponding to any particular lead will not be completed upon absence of that lead remaining portion, since the cutting and forming blade is limited in movement to prevent direct engagement with the contact fingers corresponding to that row.